Carpets having a back-coating of in situ-formed polyurethane

ABSTRACT

Carpets are back-coated with essentially non-cellular elastomeric polyurethanes, formed and cured in situ at ambient temperature from a mixture of selected polyether-polyols, selected polyisocyanates and catalyst.

United States Patent Dijkhuizen et a1. 5] May 23, 1972 54] CARPETSHAVING A BACK-COATING [56] References Cited F IN ITU-F RNIED P YUREIHANE0 s 0 0L UNITED STATES PATENTS [72] Inventors: Willem Dlikhuizen,Zuid-Laren; Pieter Johannes Adrianus Beersma Hare, both ggfrlinn..117/161 X Netherlands 3,505,252 4 1970 Brotherton et a1 ..117/161 x[73] Assignee: Scholten Research N.V., Foxhol, Netherlands FOREIGNPATENTS OR APPLICATIONS 22 F] d: M 19 1969 224,254 l/1959 Australia..161/67 1 908,188 10/1962 Great Britain ..117/161 21 App1.No.: 825,959

Primary ExaminerWilliam D. Martin Assistant ExaminerMathew R. P.Perrone,.lr. [3O] Fore'gn Application Pnomy Data Attorney-Wenderoth,Lind & Ponack May 25, 1968 Great Britain ..25,096/68 ABSTRACT [52]U.S.Cl. ..117/161 KP, 156/306, 156/328, Carpets are bacbcoated withessentially nomceuular 51/66, 61/150 elastomeric polyurethanes, fonnedand cured in situ at am- [51] Int.Cl. ..B44dl/09,D04I1l/58 biemtemperature from a mixture of Selected polyethep [58] Field ofSearch..117/161 KP; 156/306, 328;

polyols, selected polyisocyanates and catalyst.

1 1 Claims, N0 Drawings CARPETS HAVING A BACK-COATING OF IN SITU- FORMEDPOLYURETHANE The present invention relates to the application ofbackcoatings to carpets. More particularly it relates to the applicationof polyurethane coatings to the back of carpets.

When reference herein is made to carpets, it will be understood that anyfabric-like sheet material is contemplated, whether tufted, woven,knitted, felted, cemented or otherwise, and that the fabric may be acarpet, rug, mat, floor covering, floor tile, wall covering or the like.The carpet back-cloth may consist of natural and/or synthetic textilematerials, such as jute, hessian, nylon, polypropylene and the like. Thepile elements may also be built up of natural and/or synthetic textilematerials, such as wool, nylon, polyacrylonitrile, polypropylene and thelike.

Back-coating is widely used in the production of most types of carpets.Numerous related factors, including basic carpet construction,application techniques, the required characteristics of the finishedcarpet and, of course, cost determine whether to back-coat and what touse.

The main function of back-coating of carpets is adhesive.

Carpet properties which are directly effected by back-coating includethe following.

l. Tuft retention or pile lock. Whereas closely woven .car-

pets of high pile density may have adequate tuft retention without aback-coating, tufted carpets have virtually no tuft retention, unlessthey are back-coated. With a suitable back-coating their tuft retentioncan be made excellent. The tuft-retention of Wilton or Axminster carpetsof low pile density may also considerably be enhanced by back-coating.

2. Antifray properties. It is important to eliminate the fraying of cutedges of tufted carpets. To achieve complete antifray, an appreciableweight of coating is required, in order that all of the yarns in thecarpet are contacted by the coating.

Appearance of the carpet. The back-coating will give a better handle tothe carpet by introducing a certain degree of stiffness. It also affectsthe properties of the laid carpet; it prevents ruckling, imparts a highdegree of resilience and prevents slipping of the carpet on a polishedfloor.

4. Dimensional stability. By locking the fibers together and by slowingtheir moisture loss and regain, a back-coating increases the dimensionalstability of the carpet.

The back coating must have a long effectiveness. It should have a hightensile strength, it should not be dissolved by water and commonsolvents and not be affected by the components of the floor on which thecarpet is laid. it should be capable of application by simple techniquesand provide good adhesion for a secondary back-cloth.

Well known carpet backing compounds are styrene-butadiene copolymerlatices, in which the copolymers may be carboxylated or not, naturalrubber latices, emulsions of homoor copolymers of vinylacetate, acrylicacid esters and the like, and polyvinyl chloride plastisols. It has alsobeen proposed to back-coat carpets with polyurethanes, either in theform of organic solutions of prepolymers, in the form of aqueousemulsions of blocked polymers or in the form of a foaming mixture.

In all these cases the carpet coming from the carpet producing machinemust be transferred to a separate carpet backing machine. The backingmachine performs essentially two operations. The first operationconsists in distributing the coating material to the back of the carpetand the second consists in fixing permanently the coating thus appliedby drying, gelation, vulcanization, curing or the like. For the latteroperation huge dryers, usually of the hot air type, operating attemperatures up to 160 C. are needed.

An object of the present invention is to back-coat carpets withessentially non-cellular elastomeric polyurethanes, which are formed onthe back of the carpet by in situ reaction of specificpoly-ether-polyols and polyisocyanates. The

anchorage of the tufts obtained in this way is much better than withpolyurethane foam, the tensile strength of non-cellular polyurethanesbeing much higher than that of polyurethane foam.

A further object of the invention is to back-coat carpets withnon-cellular elastomeric polyurethanes, which cure in situ on the backof the carpet at ambient temperature in relatively short time thusobviating the need for a separate heating process.

A further object is to provide new polyurethane backing compounds forcarpets which give excellent tuft anchorage, antifray properties,improved handle and dimensional stability to the carpets.

Still another object is to provide novel back-coated carpets in whichthe backing material consists of selected polyurethanes, and whichpossess improved properties.

According to the method of the present invention an essentiallyanhydrous, intimate mixture of a. one or more liquid or semi-liquidpolyether-polyols containing wholly or partially secondary hydroxygroups, having hydroxyl numbers in the range of 365, and which areobtained by the addition of one or more alkylene oxides having fromthree to four carbon atoms or ethylene oxide and at least one otheralkylene oxide having three to four carbon atoms to one or morepolyhydroxyl compounds having at least three and preferably from threeto nine hydroxyl groups, and

b. one or more liquid or semi-liquid organic polyisocyanates containingat least two isocyanate groups per mol, in which the ratio between NCO-and OH-groups is within the range from about 0,95 to about 1,5 l, andone or more catalysts for the formation of polyurethanes is applied tothe back of a carpet and allowed to react in situ.

It is highly surprising that the curing of the system under thesecircumstances is almost complete, which contributes very much to thehigh strength of the new back-coatings.

The specific polyether-polyols which are used according to the inventionare obtained by the addition of alkylene oxides having from two to fourcarbon atoms to compounds having three or more active hydrogen atoms.When ethylene oxide is used for this addition reaction polyether-polyolsare formed with contain only primary hydroxyl groups. Suchpolyetherpolyols cannot be used in the present invention. When propyleneor butylene oxides are used for the addition reaction, acid catalystsfor the addition tend to produce polyetherpolyols having partly primaryand secondary hydroxyl-groups in their molecules. Thesepolyether-polyols, carrying both primary and secondary hydroxyl groups,are preferably used as the polyol component in the back-coating mixtureaccording to the invention.

Any of the acid catalyst which have been employed to carry out alkyleneoxide additions may be used to prepare the polyethers. Typical acidcatalysts, which are preferably used in our invention are mineral acidsor Lewis acid catalysts, such as boron trifluoride, tribromide oftrichloride, and the chlorides of aluminium tin, iron and zinc. Inaddition, complexes of Lewis acid catalysts and other organic orinorganic compounds may also be used.

Particularly effective catalysts have proved to be boron trifluoride andits complexes. The amount of catalysts used in the condensation is notcritical. An operable range is from 0,l to 1,0 percent, based on theweight of the polyether reaction mixture. The residual acid constituentsin the polyether ob- 'tained may be left therein as such or they may bepartially or be used as such in the process according to the invention.In a preferred embodiment of the invention such polyether-polyols areapplied after a part of their secondary hydroxyl groups have been cappedwith hydroxyethyl groups through reaction with ethylene oxide. Thesimultaneous presence of secondary and primary hydroxyl groups in thepolyether-polyols thus obtained improves the results to be obtained bythe present invention.

The hydroxyl number of the polyether-polyols should be within the rangeof 100 to 365 and preferably in the range of 200 to 300. Thepolyether-polyol should be of a liquid or semiliquid nature at ambienttemperatures or slightly above that.

Typical polyhydroxyl compounds suitable as starting materials for thepreparation of the polyethers are triols, such as glycerol, trimethylolpropane and hexanetriol, tetrols, such as erythritol andpentaerythritol, pentols, such as arabitol and xylitol, hexols, such assorbitol and mannitol, glycosides, such as methyl glucoside, ethyleneglycol glucoside and glycerol glucoside and monoand polysaccharides,such as arabinose, glucose, sucrose, lactose, dextrin and starch. Ingeneral polyhydroxyl compounds with cylic nulei are preferred, sincethey yield polyurethane resins with outstanding properties.

Mixtures of these polyhydroxyl compounds may also be used. Thesepolyhydroxyl compounds are preferably reacted in a substantially drystate with the alkylene oxide, although small amounts of water may bepresent.

The alkylene oxides which may be reacted with the polyhydroxyl compoundsto form the polyether useful in this invention are those which have fromtwo to four carbon atoms, such as ethylene oxide, propylene oxide,l,2-butylene oxide, 1,3-butylene oxide, 2,3-butylene oxide andisobutylene oxide. These alkylene oxides may be used singly (with theexception of ethylene oxide) or in admixture. Propylene oxide is thepreferred alkylene oxide in our invention. Since ethylene oxide producespolyethers containing only primary hydroxylgroups, this alkylene oxideis only used together with other alkylene oxides. It is employed inrelatively low quantities in order to introduce the desired amount ofprimary hydroxyl groups in polyether-polyols which otherwise do notcontain primary hydroxyl groups.

Representative examples of organic polyisocyanates containing at leasttwo isocyanate groups per mol are all those which are liquid orsemi-liquid under the conditions of use. For this reason it may benecessary to apply heat to certain polyisocyanates, in order to raisetheir temperature above their melting points, or to add a minor amountof a solvent. The liquid or semi-liquid, melted polyisocyanate may thenbe mixed with the polyether.

I Suitable organic polyisocyanates include 2,4 tolylene diisocyonate,2,6 tolylene diisocyanate, commercially available mixtures containing 65or 80 percent of 2,4 tolylene diisocyanate and 35 or percent of 2,6tolylene diisocyanate, 1,3 benzene diisocyanate, 1,4 benzenediisocyanate, technical or pure 4,4 diphenylmethane diisocyanate,polymethylene polyphenylisocyanate, 3,3'dimethyl diphenylmethanediisocyanate and l, l-diphenylcyclclohexyl 4,4-diisocyanate. Instead ofthe simple polyisocyanates, it is possible to use liquid or semi-liquidprepolymers, especially those which contain predetermined proportions ofthe selected polyethers. Furthermore polyfunctional isocyanates whichare produced from polyisocyanates and water with biuret formation arealso to be considered, e.g. a liquid triisocyanate obtained from 3 molsof hexamethylene diisocyanate and 1 mol of water. Polycarbodiimides withterminal free isocyanate groups are also suitable. Due to their lowvapor pressure and resulting low toxicity the liquid or semi-liquidpolyvalent polyisocyanates having an average functionality higher than 2are preferred.

Mixtures of polyisocyanates may likewise be employed. In case theacidity of the polyisocyanate is too high, it may be necessary toneutralize the acid residues by addition of basic compounds, such astertiary amines.

In accordance with this invention the polyether containing hydroxylgroups and the polyisocyanate are used in relative amounts correspondingto a NCO/OH ratio within the range of 0,95164 to 1,5. 0,95 NCO/OH ratiosoutside these limits, the physical properties of the polyurethane resinsare generally somewhat less good. Preferably the NCO/OH ratio is fromabout 1,01 to 1,20.

The catalysts which are needed to make the reaction mixture curable atambient temperatures comprise organometal compounds or metal salts ofcarboxylic acids derived from polyvalent metals such as tin, cobalt,lead, cadmium, titane, and zinc. Typical of such catalysts aredibutyltin dilaurate, dibutyltin di-2-ethylhexoate, dibutyltindiversatate, stannous octoate and the like. These catalysts may bepresent in amounts ranging from 0,05 to 2,0 percent based on the weightof the reaction mixture. They are advantageously used in combinationwith amine type catalysts, such as triethylene diamine,tetramethylbutane diamine and the like.

The intimate mixture of the reactants is made by pumping said reactantsor premixed compounds thereof to the mixing chamber of a commercialpolyurethane machine from where it is dispensed in the form of fineparticles or as a thin layer, for instance, by means of a sprayingnozzle. It is evenly deposited on the back of the carpet to be coated,where it is left to cure. Within a couple of minutes the coating willhave lost its tack and the carpet may be stored by winding the same onrollers. If desired, the back-coated carpet, while still being in atacky state, may be contacted with a second layer of hessian or burlap.The sandwich is then passed through a pair of nip rollers and allowed tocure. In this way a secondary cloth-back with a very neat appearance isobtained.

It should be noted that in order to get the best performance of thepolyurethane resin, the reaction mixture which forms the polyurethaneelastomer should not substantially foam. Since water reacts withisocyanates with formation of carbon dioxide, its content should be aslow as possible. Therefore the reactants should be virtually anhydrousand it is desirable to include a water scavenger in the reactionmixture, such as molecular sieves, hydrolysable esters or the like, likeorthoformic acid esters or titanic acid esters.

Other substances, which may be added to the reaction mixture arepigments, fillers, plasticizers, anti oxidants, surfactants, stabilizersand the like. The surfactants, for instance, may be added in order toincrease the penetration of the polyurethane in the backing cloth andaround the piles so as to firmly bond the pile to the backing cloth. Insome instances small amounts of diluting agents, which decrease theviscosity of the reaction mixture, may also be added to increase thepenetration. These agents will not perform as blowing agents, because ofthe thin layers which are applied to the back of the carpet, a usualcoating consisting of about 200 250 g polyurethane mix per m Theback-coated carpets made according to the invention exhibit a very goodtuft anchorage, and have a pleasant handle and a desirable flexibility.The abrasion resistance and the dimensional stability is very high asshown by wear trials. The carpets perfectly withstand a heat ageing testand have a distinct chemical inertness.

The following examples illustrate various embodiments of this invention.The parts referred to are by weight.

EXAMPLE I A mixture is prepared according to the following formula: 75parts of an acid catalyzed dextrose and propylene oxide based polyol,hydroxyl-number 280, containing secondary and primary hydroxyl groups2,2 parts of sodium aluminium silicate 0,4 part of dibutyltindiversatate 0,35 part of tetramethylbutane diamine This premixedcompound is pumped into the mixing head of a two-component polyurethanespraying device.

The other component consists of 64,2 parts of 4,4'-diphenylmethanediisocyanate. The reaction mixture is deposited on the back of a tuftedcarpet consisting of jute back-cloth and nylon piles, in an amount of250 g/m". The reaction mixture reacts and cures at ambient temperaturein a couple of minutes, to yield a back coated carpet. The anchorage ofthe tufts in the carpet and the wear resistance of the carpet are verygood.

EXAMPLE 2 A premix is made of the following ingredients 100 parts of anacid catalyzed starch and propylene oxide based polyol, hydroxyl-number220, containing secondary and primary hydroxyl groups 5 parts ofmethylene chloride 3 parts of sodium aluminium silicate 0,4 part ofdibutyltin dialurate 0,4 part of tetramethylbutane diamine. Thiscompound is fed as one component to a two component spraying gun, theother component consisting of 56 parts of 4,4'-diphenylmethanediisocyanate. The mixture is sprayed on a polypropylene fabric tuftedwith polypropene yarns. lt cures in situ in a very short time at ambienttemperature. The adhesion of the polyurethane to the mat is excellent.The tuft anchorage is very good.

EXAMPLE 3 A mixture of the following composition is prepared: 100 partsof a base catalyzed addition product of glycerol and propylene oxide,hydroxyl numer 260.

5 parts of methylene chloride 0,4 part of dibutyltin diversatate 0,35part of tetramethylbutane diamine.

This mixture is pumped into the mixing head of a two-componentpolyurethane spraying device. The other component consists of 67,1 partsof 4,4-diphenylmethane diisocyanate. The reaction mixture is sprayed onthe back of a tufted carpet consisting of jute cloth and nylon looppiles in an amount of 320 g/m Another jute cloth is contacted with thetacky reaction mixture and the secondary backed carpet is passed througha pair of nip rollers and allowed to cure at ambient temperature.

The average tuft bind as measured by a dynamometer is 6,2 kg per loop.The adhesion of the secondary back cloth is rather good. When thepolyetherpolyol is replaced by an ethylene oxide cappedhydroxypropylether of glycerol with hydroxyl number 260 the average tuftbind is 6,8 kg per loop, whereas the addition of the secondary backcloth also has improved.

We claim l. Back-coated carpet comprising tufted carpet with a backingmaterial consisting essentially of 200-320 g/m of a substantiallynon-cellular elastomeric polyurethane as the in situ product of reactionof a substantially anhydrous mixture of a liquid or semi-liquidpolyether polyol containing secondary hydroxyl groups and having ahydroxyl number of to 365 selected from the group consisting of additionproducts of a polyhydroxyl compound having from three to nine hydroxylgroups and an alkylene oxide having from three to four carbon atoms,addition products of a polyhydroxyl compound having from three to ninehydroxyl groups, an alkylene oxide having from three to four carbonatoms and ethylene oxide, and mixtures of such addition products, and anaromatic polyisocyanate selected from the group consisting of2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-benzenediisocyanate, 1,4-benzene diisocyanate, 4,4-diphenylmethanediisocyanate, polymethylene polyphenylisocyanate, 3,3- dimethyldiphenylmethane diisocyanate, 1,1-diphenylcyclohexyl-4,4-diisocyanateand mixtures thereof, the ratio between NCO groups and OH groups beingwithin the range 2. The carpet according to claim 1 in which thepolyetherpolyol also contains primary hydroxyl groups and has beenobtained by an acid catalysed addition of one or more alkylene oxideshaving from three to four carbon atoms to one or more polyhydroxylcompounds having from three to nine hydroxyl groups.

3. The carpet according to claim 1 in which the polyetherpolyol alsocontains primary hydroxyl groups and has been obtained by capping apolyether-polyol which contains strictly secondary hydroxyl groups withethylene oxide.

4. The carpet according to claim 1 in which the alkylene oxide ispropylene oxide.

5. The carpet according to claim 1 in which the polyhydroxyl compoundcontains a cyclic nucleus.

6. The carpet according to claim 5 in which the polyhydroxyl compound isa glycoside, a monosaccharide or a polysaccharide.

7. The carpet according to claim 1 in which the polyisocyanate is4,4'-diphenylmethane diisocyanate.

8. The carpet according to claim 1 in which the ratio between NCO-groupsand OH-groups is from about 1.01 to about 1.20: l.

9. The carpet according to claim 1 in which the intimate mixture of oneor more polyether-polyols, polyisocyanates and catalysts is allowed tocure at ambient temperature.

10. The carpet according to claim 1 in which the intimate mixture of oneor more polyether-polyols, polyisocyanates and catalysts also contains awater scavenger.

11. Back-coated carpets according to claim 1, tufted with average tuftbond of at least 6.2 kg per loop.

2. The carpet according to claim 1 in which the polyether-polyol alsocontains primary hydroxyl groups and has been obtained by an acidcatalysed addition of one or more alkylene oxides having from three tofour carbon atoms to one or more polyhydroxyl compounds having fromthree to nine hydroxyl groups.
 3. The carpet according to claim 1 inwhich the polyether-polyol also contains primary hydroxyl groups and hasbeen obtained by capping a polyether-polyol which contains strictlysecondary hydroxyl groups with ethylene oxide.
 4. The carpet accordingto claim 1 in which the alkylene oxide is propylene oxide.
 5. The carpetaccording to claim 1 in which the polyhydroxyl compound contains acyclic nucleus.
 6. The carpet according to claim 5 in which thepolyhydroxyl compound is a glycoside, a monosaccharide or apolysaccharide.
 7. The carpet according to claim 1 in which thepolyisocyanate is 4,4''-diphenylmethane diisocyanate.
 8. The carpetaccording to claim 1 in which the ratio between NCO-groups and OH-groupsis from about 1.01 to about 1.20 :
 1. 9. The carpet according to claim 1in which the intimate mixture of one or more polyether-polyols,polyisocyanates and catalysts is allowed to cure at ambient temperature.10. The carpet according to claim 1 in which the intimate mixture of oneor more polyether-polyols, polyisocyanates and catalysts also contains awater scavenger.
 11. Back-coated carpets according to claim 1, tuftedwith average tuft bond of at least 6.2 kg per loop.